(1) The lens must be cleaned daily:

Bend the lens cleaning paper into several folds and soak it with a few drops of analytical pure acetone; Gently wipe the lens surface with wet lens paper, and pay attention not to press the lens with your fingers; Repeat several times until the lens surface is clean and free of dirt and residual traces; Dry with dry air; If necessary, roll the lens paper wet with a few drops of acetone into a rod, and gently scrub the lens surface to remove heavy dirt drops.

(2) Mirror lenses should also be cleaned regularly to remove dirt:

Remove the lens from the frame; With the mirror face up, put the lens paper on the mirror; Drop a few drops of acetone on the lens paper, and gently pull the lens paper over the mirror; Repeat the above procedures until the mirror is clean and free of dirt and residue; Then install the lens into the lens base.